Porous devices and processes for producing same

ABSTRACT

Devices and methods for making a polymer with a porous layer from a solid piece of polymer are disclosed. In various embodiments, the method includes heating a surface of a solid piece of polymer to a processing temperature and holding the processing temperature while displacing a porogen layer through the surface of the polymer to create a matrix layer of the solid polymer body comprising the polymer and the porogen layer. In at least one embodiment, the method also includes removing at least a portion of the layer of porogen from the matrix layer to create a porous layer of the solid piece of polymer.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of co-pending U.S. patentapplication Ser. No. 16/524,541, filed Jul. 29, 2019, which iscontinuation of U.S. patent application Ser. No. 15/854,746, filed Dec.26, 2017, now U.S. Pat. No. 10,405,962, which is a continuation of U.S.patent application Ser. No. 15/362,223, filed Nov. 28, 2016, now U.S.Pat. No. 9,848,973, which is a continuation of U.S. patent applicationSer. No. 14/752,762, filed Jun. 26, 2015, now U.S. Pat. No. 9,504,550,which is a continuation-in-part of U.S. patent application Ser. No.14/587,856, filed Dec. 31, 2014, now U.S. Pat. No. 9,085,665; and whichclaims the benefit under 35 U.S.C. 119 of, and priority to, U.S.Provisional Patent Application No. 62/017,834, filed Jun. 26, 2014, eachof which are incorporated herein by reference in their entireties.

This application incorporates by reference herein the following patentapplications: U.S. patent application Ser. No. 12/997,343, entitled“Material and Method for Producing the Same,” filed on Jan. 19, 2011;U.S. patent application Ser. No. 13/558,634, entitled “Porous Materialand Method for Producing the Same,” filed on Jul. 26, 2012; U.S. patentapplication Ser. No. 12/997,343, entitled “Material and Method forProducing the Same,” filed on Jan. 19, 2011; International PatentApplication (PCT) No. PCT/US2009/047286, entitled “Material and Methodfor Producing the Same,” filed on Jun. 12, 2009; International PatentApplication (PCT) No. PCT/US2013/055656, entitled “Systems and Methodsfor Making Porous Films, Fibers, Spheres, and Other Articles,” filed onAug. 20, 2013; and International Patent Application (PCT) No.PCT/US2013/055655, entitled “Particulate Dispensing Apparatus,” filed onAug. 20, 2013.

TECHNICAL FIELD

The present disclosure relates generally to devices with porous surfacesand processes for creating porous polymers.

BACKGROUND

Polymers have been shown to have many advantageous mechanical andchemical properties such as imperviousness to water, low toxicity,chemical and heat resistance, and shape-memory properties. Additionally,polymers are often relatively low cost, easy to manufacture, andversatile in application. These characteristics have led to the use ofpolymers in many applications such as, for example, medical devices,electronics, optics, computing, and a wide-array of consumer products.

Adding pores to one or more surfaces of a polymer structure may providefurther advantages, such as, for example, increasing friction at the oneor more porous surfaces and providing better device integration insurgical applications by promoting adjacent tissue ingrowth. However, aswill be understood by one of ordinary skill in the art, introducingporosity into polymers may, in some instances, weaken desired mechanicalproperties, such as shear strength at the porous surface. Thus, althoughintroducing pores into such polymers may have certain advantages, it hasbeen limited in application due to a loss in mechanical properties.

BRIEF SUMMARY OF THE DISCLOSURE

One aspect of the present disclosure generally relates to producing aporous surface from a solid piece of polymer. In particular, producing aporous surface from a solid piece of polymer at a processing temperaturebelow a melting point of the polymer to produce a solid piece of polymerwith a porous surface integrated into the solid piece of polymer.

In a particular aspect, the present disclosure generally relates toproducing a porous surface from a piece of polymer with shear strengththat increases substantially linearly with processing time. In someaspects, the present disclosure relates to a method for forming a solidpolymer body with pores distributed through at least a portion of thesolid polymer body, the method comprising: A) heating a surface of asolid piece of polymer to a processing temperature below a melting pointof the polymer; and B) holding the processing temperature whiledisplacing a porogen layer through the surface of the polymer to createa matrix layer of the solid polymer body comprising the polymer and theporogen layer. This particular embodiment may further include aprocessing temperature that is about one to thirty-eight degrees Celsiusless than the melting point of the polymer.

According to various aspects, the present disclosure relates to a methodfor forming a solid polymer body with pores distributed through at leasta portion of the solid polymer body, the method including: A) placing asurface of a solid piece of polyetheretherketone (PEEK) in contact witha portion of a plurality of sodium chloride grain layers; B) heating thesurface of the solid piece of PEEK to a processing temperature of about305 to 342 degrees Celsius; C) holding the processing temperature of thesurface of the solid piece of PEEK for a processing period of time ofbetween about twenty and forty minutes to create a viscous layer of PEEKfrom the solid piece of PEEK; D) displacing at least the portion of theplurality of sodium chloride grain layers through the viscous layer ofthe solid piece of PEEK, creating a matrix layer of PEEK and sodiumchloride grains; and E) leaching one or more of the chloride grains ofthe plurality of sodium chloride grain layers and cooling the surface ofthe solid piece of PEEK to form a solid polymer with a porous layer,wherein a shear strength of the porous layer increases substantiallylinearly with the processing period of time.

Particular aspects of the present disclosure relate to a methodincluding: A) heating a surface of a solid polyetheretherketone (PEEK)body to a maximum processing temperature that is below a meltingtemperature of the surface of the solid PEEK body by a meltingtemperature differential; B) displacing a plurality of layers of aporogen through the surface and into a defined distance of the solidPEEK body, creating, thereby, a matrix layer including PEEK and theplurality of layers of the porogen, the matrix layer being integrallyconnected with the solid PEEK body; C) maintaining throughout theheating and displacing steps, a temperature of the surface of the solidPEEK body that is below the melting temperature by at least the meltingtemperature differential; and D) removing a portion of the plurality oflayers of porogen from the matrix layer, creating, thereby, a porousPEEK layer integrally connected with a remaining portion of the solidPEEK body.

According to at least one aspect, a method, including: A) heating asurface of a solid polyetheretherketone (PEEK) body to a maximumprocessing temperature that is below a melting temperature of thesurface of the solid PEEK body by a melting temperature differential; B)displacing a plurality of layers of a porogen through the surface andinto a defined distance of the solid PEEK body, creating, thereby, amatrix layer including PEEK and the plurality of layers of the porogen,the matrix layer being integrally connected with the solid PEEK body; C)maintaining throughout the heating and displacing steps, a temperatureof the surface of the solid PEEK body that is below the meltingtemperature by at least the melting temperature differential; and D)removing a portion of the plurality of layers of porogen from the matrixlayer, creating, thereby, a porous PEEK layer integrally connected witha remaining portion of the solid PEEK body, wherein the temperaturedifferential is between one degree Celsius and thirty-eight degreesCelsius.

According to some aspects, a method for forming a solid thermoplasticbody with pores distributed through at least a portion of the solid, themethod including: A) heating a surface of a solid piece of thermoplasticto a processing temperature below a melting point of the thermoplastic;B) holding the processing temperature below a melting point of thethermoplastic while displacing the surface of the thermoplastic througha granular porogen layer to create a matrix layer of the solidthermoplastic body including the thermoplastic and the porogen layer;and C) cooling the matrix layer to cease displacement of the granularporogen through the thermoplastic.

According to one or more aspects, a medical device for promoting tissueingrowth, the medical device including a solid thermoplastic bodyincluding: A) a body layer, the body layer including a thermoplasticwith crystallites varying in size; and B) a porous surface layer of thebody, the porous surface layer of the body including irregular,substantially spherical pores extending through the solid thermoplasticbody for a defined distance, wherein the interfacial shear strengthbetween the body layer and the porous surface layer is at least about 17MPa.

According to various aspects, a medical device for promoting tissueingrowth, the medical device including a solid thermoplastic bodyincluding: A) at least two porous surface layers that are on oppositefaces of the solid thermoplastic body, the at least two porous surfacelayers including irregular, substantially spherical pores extendingthrough the solid thermoplastic body for a defined distance; and B) abody layer that is between the at least two porous surface layers, thebody layer including a thermoplastic with crystallites varying in size,wherein: i) the at least two porous surface layers include an increasedpercentage of hydroxyl groups in comparison to the body layer; ii) acarbon to oxygen atomic ratio of the at least two porous surface layersis substantially the same as a carbon to oxygen atomic ratio of the bodylayer; iii) the at least two porous surface layers have increasedwettability in comparison to the body layer; and iv) theinterconnectivity of the irregular, substantially spherical pores isabout 99%.

According to a particular aspect, a method, including: A) heating asurface of a solid polyetheretherketone (PEEK) body to a processingtemperature that is above a glass transition temperature of PEEK; B)displacing a plurality of layers of a porogen through the surface andinto a defined distance of the solid PEEK body; C) cooling the surfaceof the solid PEEK body at a predetermined rate; and D) removing aportion of the plurality of layers of porogen from the surface,creating, thereby, a porous PEEK layer integrally connected with aremaining portion of the solid PEEK body and including: i) an increasedpercentage of hydroxyl groups in comparison to a percentage of hydroxylgroups in the solid PEEK body; ii) a carbon to oxygen atomic ratio thatis substantially the same as a carbon to oxygen atomic ratio of thesolid PEEK body; and iii) an increased wettability in comparison to thesolid PEEK body.

According to at least one aspect, medical device for promoting tissueingrowth, the medical device including a thermoplastic body defining aporous surface formed from a plurality of substantially spherical pores,each of the pores extending a defined distance from the top face intothe body, wherein: A) the porous surface has a particular wettability,wherein the particular wettability is greater than a wettability of thebody; and B) an interconnectivity between the plurality of substantiallyspherical pores is at least 99%.

According to some aspects, a method for determining tissue ingrowth intoa medical device, the method including: A) providing a medical deviceincluding: i) a radiolucent material; ii) a porous surface; and iii) atleast one tantalum marker for detecting the medical device in aradiograph, wherein a top of the tantalum marker is approximately flushwith a top of the porous surface; and B) instructing one or moreclinicians to: i) take a radiograph of the medical device, wherein themedical device is implanted in a patient; and ii) measure the distancebetween the patient's tissue and the top of the at least one tantalummarker, thereby determining the tissue ingrowth of the patient's tissueinto the medical device.

These and other aspects, features, and benefits of the claimed systemsand methods will become apparent from the following detailed writtendescription of the preferred embodiments and aspects taken inconjunction with the following drawings, although variations andmodifications thereto may be effected without departing from the spiritand scope of the novel concepts of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exemplary flow chart of an exemplary process for creating aporous polymer, according to one embodiment.

FIG. 2 illustrates an exemplary process for creating a porous polymer,according to one embodiment.

FIG. 3 is an exemplary graph showing results of a differential scanningcalorimetry scan of polyetheretherketone (PEEK) showing exemplaryendotherms of PEEK under particular conditions, according to oneembodiment.

FIG. 4A is an exemplary plot graph showing exemplary shear strengthproperties of PEEK over time under particular conditions, according toone embodiment.

FIG. 4B is an exemplary bar graph showing exemplary shear strength overtime under particular conditions, according to one embodiment.

FIG. 4C is an exemplary plot graph showing exemplary pressure versestime data of PEEK under certain conditions, according to one embodiment.

FIG. 4D is an exemplary bar graph showing exemplary pressure verses timedata of PEEK under certain conditions, according to one embodiment.

FIG. 5A is an exemplary plot graph showing exemplary shear strengthproperties of PEEK over time under particular conditions, according toone embodiment.

FIG. 5B is an exemplary bar graph showing exemplary shear strengthproperties of PEEK over time under particular conditions, according toone embodiment.

FIG. 5C is an exemplary plot graph showing exemplary pressure versestime data of PEEK under certain conditions, according to one embodiment.

FIG. 5D is an exemplary bar graph showing exemplary pressure verses timedata of PEEK under certain conditions, according to one embodiment.

FIG. 6A is an exemplary XPS O1s spectra of an injection molded porouspolymer under certain conditions, according to one embodiment.

FIG. 6B is an exemplary XPS O1s spectra of surface porous polymer undercertain conditions, according to one embodiment.

FIG. 6C is an exemplary XPS O1s spectra of surface porous polymer aftergamma sterilization under certain conditions, according to oneembodiment.

FIG. 6D is an exemplary table comprising exemplary XPS O1s spectraratios under certain conditions, according to one embodiment.

FIG. 6E is an exemplary table comprising exemplary XPS O1s elementalratios under certain conditions, according to one embodiment.

FIG. 7A is an exemplary table comprising exemplary contact angles of aporous polymer under certain conditions, according to one embodiment.

FIG. 7B is an exemplary table comprising exemplary roughness data of apolymer under certain conditions, according to one embodiment.

FIG. 8A is an exemplary bar graph showing hydroxyl group percentages ofa polymer verses processing temperature under certain conditions,according to one embodiment.

FIG. 8B is an exemplary bar graph showing hydroxyl group percentages ofa polymer verses processing pressure under certain conditions, accordingto one embodiment.

FIG. 8C is an exemplary bar graph showing hydroxyl group percentages ofa polymer verses processing substrate under certain conditions,according to one embodiment.

FIG. 8D is an exemplary bar graph showing hydroxyl group percentages ofa polymer verses cooling rate under certain conditions, according to oneembodiment.

FIG. 8E is an exemplary bar graph showing hydroxyl group percentages ofa polymer verses processing temperature under certain conditions,according to one embodiment.

FIG. 9A is an exemplary bar graph showing exemplary porous layerdimensions of a polymer under certain conditions, according to oneembodiment.

FIG. 9B is an exemplary bar graph showing exemplary porous layerproperties of a polymer under certain conditions, according to oneembodiment.

FIG. 10 is an exemplary bar graph showing exemplary expulsion loadverses structure of a polymer under certain conditions, according to oneembodiment.

FIG. 11A is a top view of a non-limiting, exemplary embodiment of amedical device, according to one embodiment.

FIG. 11B is a sectional view of a non-limiting, exemplary embodiment ofa medical device, according to one embodiment.

FIG. 11C is a side view of a non-limiting, exemplary embodiment of amedical device, according to one embodiment.

DETAILED DESCRIPTION

Whether or not a term is capitalized is not considered definitive orlimiting of the meaning of a term. As used in this document, acapitalized term shall have the same meaning as an uncapitalized term,unless the context of the usage specifically indicates that a morerestrictive meaning for the capitalized term is intended. However, thecapitalization or lack thereof within the remainder of this document isnot intended to be necessarily limiting unless the context clearlyindicates that such limitation is intended. Further, one or morereferences are incorporated by reference herein. Any incorporation byreference is not intended to give a definitive or limiting meaning of aparticular term. In the case of a conflict of terms, this documentgoverns.

For the purpose of promoting an understanding of the principles of thepresent disclosure, reference will now be made to the embodimentsillustrated in the drawings and specific language will be used todescribe the same. It will, nevertheless, be understood that nolimitation of the scope of the disclosure is thereby intended; anyalterations and further modifications of the described or illustratedembodiments, and any further applications of the principles of thedisclosure as illustrated therein are contemplated as would normallyoccur to one skilled in the art to which the disclosure relates. Alllimitations of scope should be determined in accordance with and asexpressed in the claims.

Overview

According to particular embodiments, the systems and methods herein aredirected to a process for producing a porous polymer including: 1)heating a surface of a solid piece of polymer to a processingtemperature; 2) holding the processing temperature while displacing aporogen layer through the surface of the polymer to create a matrixlayer of the solid polymer body including the polymer and the porogenlayer; 3) cooling the surface of the polymer; and 4) removing at least aportion of the porogen layer from polymer. The processing temperaturemay be any suitable processing temperature, including a processingtemperature below a melting point of the polymer. Further, as will beunderstood by one of ordinary skill in the art, different polymers mayhave different melting temperatures and some polymers may exhibitmelting properties at more than one temperature.

Generally, this process results in a polymer with a porous surface layeron at least one surface of the polymer body. In various embodiments, theatomic ratio of carbon to oxygen in the porous surface layer issubstantially the same as the atomic ratio of carbon to oxygen in thepolymer body. In one or more embodiments, the porous surface layer hasan increased percentage of hydroxyl groups in comparison to the polymerbody. Accordingly, in one embodiment, the process is not be an additionreaction but instead is a reduction of a carbonyl and/or ether group toa hydroxyl group.

In one or more embodiments, the increased percentage of hydroxyl groupsin the porous surface layer results in a more hydrophilic surface incomparison to unprocessed, smooth polymer. Thus, in various embodiments,the wettability of the porous surface layer is greater than thewettability of the unprocessed polymer body.

This process may also result in interfacial shear strength between theporous layer and solid polymer body that increases with longerprocessing times that are above a predetermined processing temperature(Tp), but below a melting point of the polymer. Further, pressureapplied to exert polymer flow at a constant rate is significantlycorrelated statistically (i.e. p-value less than 0.05 as calculated bylinear regression analysis) with processing time above a definedprocessing temperature of 330 degrees Celsius for up to 30 to 45minutes. This correlation is counter to expected results and indicatesthat polymer flow viscosity increases with increased processing timebelow PEEK's melting point of 343 degrees Celsius (e.g., increasedprocessing time at about one to 13 degrees below 343 degrees Celsius, orbetween about 330 and 342 degrees Celsius).

As a particular example, it has been shown that PEEK increases inviscosity over time for particular processing temperatures. Continuingwith this particular example, a sample of PEEK that is heated to aprocessing temperature of about 340 degrees Celsius has a viscosity ofabout 47,000 Pa*s at zero seconds, but increases to about 106,000 Pa*sat about 1800 seconds if this processing temperature is heldsubstantially constant. Similarly, continuing with this example, asample of PEEK that is heated to a processing temperature of about 360degrees Celsius has a viscosity of about 2,600 Pa*s at zero seconds, butincreases to about 3,200 Pa*s at about 1800 seconds if this processingtemperature is held substantially constant.

The porous surface layer may include any suitable features based on itsintended application. For example, the porous surface layer, in variousembodiments, may be between about 0.55 mm and 0.85 mm thick. In aparticular embodiment, the porous surface layer may be approximately 0.7mm thick. Similarly, the struts, which define the shape of the pores inthe porous surface layer, may be spaced between about 0.21 mm and 0.23mm apart with a thickness of between about 0.9 mm and 0.11 mm.Throughout the porous surface layer, in a particular embodiment, theporosity is between about 61% and 66% and the interconnectivity of thepores may be about 99%.

The above-described process may be used to create a spinal implant ofsubstantially cubic shape with a porous layer on the top and bottomsurfaces with any of the exemplary physical or chemical propertiesdiscussed above. Generally, the spinal implant may, because of thewettability of the porous layers, promote adhesion of proteins that thenpromote tissue ingrowth. Further, the spinal implant may, because of thetopographical features of the porous layer, promote tissue ingrowth.Moreover, cylindrical markers may be inserted into the spinal implant sothat the amount of tissue ingrowth may be visualized using standardelectromagnetic-imaging techniques.

As will be understood by one of ordinary skill in the art, “polymerflow” or “polymer flow viscosity”, as used herein may refer to any flowof a particular polymer and may not necessarily mean flow of a polymerabove a melting point of the particular polymer (although, in someembodiments, polymer flow, as discussed herein, may refer to flow of aparticular polymer above a melting point of the particular polymer). Inspecific embodiments, “polymer flow” and “polymer flow viscosity” referto flow of a polymer below a melting point of the polymer. Alternately,polymer flow or polymer flow viscosity may be referred to as “polymerresistance to displacement” or the like.

As will be understood by one of ordinary skill in the art, any suitablematerials may be used in the above process or in the above-describeddevices. In at least one embodiment, the polymer in the above exemplaryprocess is polyetheretherketone (PEEK). In one or more embodiments, theporogen in the above exemplary process is sodium chloride grainsarranged in one or more layers, such that when the polymer is heated itat least partially flows between the gaps of the layers of the sodiumchloride particles.

Exemplary Process

Turning now to FIG. 1, an exemplary process for producing a porouspolymer is shown. This exemplary process begins at step 110 by heating asurface of a solid piece of polymer to a processing temperature below amelting point of the polymer. In various embodiments, the surface isheated in any suitable way, such as by conductive heating, microwaveheating, infrared heating, or any other suitable heating method.

Any surface of the solid piece of polymer may be heated. In a particularembodiment shown in FIG. 2, a bottom surface is placed in contact with aporogen layer and heated such that the porogen layer is at leastpartially displaced within the bottom surface. In various embodiments, atop or side surface is placed in contact with a porogen layer and/orheated such that the porogen layer is at least partially displacedwithin the top or side surface. As will be understood by one of ordinaryskill in the art, a “surface” of the solid piece of polymer may be anysuitable portion (or all surfaces) of the solid piece of polymer and, inat least one embodiment, is the entire piece of polymer.

The solid piece of polymer may be any suitable material. In a particularembodiment, the polymer is polyetheretherketone (PEEK). In variousembodiments, the polymer is any other suitable thermoplastic withsimilar properties as PEEK, such as any polymer with multiple endothermsand/or broad endotherms and/or any polymer that exhibits flow above theglass transition. The polymer may be, for example, carbon fiberreinforced PEEK, polymethylmethacrylate (PMMA), polycarbonate (PC),polyphenylsulfone (PPSU), polyphenylenesulfide (PPS), polyethersulfone(PES), polyparaphenylene (also known as self-reinforcing polyphenyleneor SRP), or thermoplastic polyurethane (TPU).

The processing temperature may be any suitable temperature and maydepend upon the melting point for the particular polymer. In aparticular embodiment, the polymer is PEEK, with a melting point ofabout 343 degrees Celsius. In these embodiments (and others), theprocessing temperature may be any suitable range below the melting pointof PEEK (e.g., 343 degrees Celsius). In one or more embodiments, asdiscussed below, the processing temperature is about one (1) to 38degrees below the melting point of PEEK (e.g., the processingtemperature is approximately 305 to 342 degrees Celsius). In at leastone embodiment, the processing temperature is about 330 degrees Celsiusfor PEEK. In another embodiment, the processing temperature is about 340degrees Celsius for PEEK. As will be understood by one of ordinary skillin the art, the processing temperature, in particular embodiments, isthe processing temperature of the polymer surface.

At step 120, the process continues with holding the processingtemperature while displacing a porogen layer through the surface of thepolymer to create a matrix layer of the solid polymer body including thepolymer and the porogen layer. In various embodiments, the porogen layerincludes particles of one or more particular materials such as sodiumchloride grains or other salts, sugars, polymers, metals, etc.

The particles of the porogen layer may be arranged in any suitable way.In various embodiments, the particles of the porogen layer are arrangedin a regular lattice pattern, with each particle touching at least oneother particle. In some embodiments, the particles of the porogen layerare arranged in an irregular geometric pattern and/or are packet downwithout a planned geometric pattern.

Further, the particles of the porogen layer may be of any suitable sizeand shape. In particular embodiments, the particles of the porogen layermay be pre-processed such that they are one or more specific shapes,such as substantially spherical, substantially cubic, etc. In at leastone embodiment the particles of the porogen layer are packed, irregulargrains of a salt.

In various embodiments, the porogen layer is displaced through thesurface of the polymer by holding the processing temperature by applyingpressure to the polymer to force the polymer (which may be viscous fromheating, as discussed herein) through gaps between the porogen layer(e.g., the porogen is packed and arranged such that there are gapsbetween the particles). In at least one embodiment, the result is amatrix layer with polymer in gaps between the particles of the porogenlayer.

In embodiments where the porogen layer is located at a side surface ormore than one surface of the piece of polymer, pressure may be appliedin one or more directions to the solid piece of polymer. In one or moresuch embodiments, pressure may be applied to all sides of the solidpiece of polymer (e.g., to create a structure with more than one poroussurface).

The porogen layer may be displaced through the surface of the polymer toany suitable depth. In a particular embodiment, the porogen layer isdisplaced through the surface of the polymer to a depth of approximately0.2 mm to 2.0 mm.

At step 130, the process continues with removing at least a portion ofthe porogen layer from the matrix layer to form a solid polymer with aporous layer. As will be understood by one of ordinary skill in the art,the portion of the porogen layer to be removed may be removed in anysuitable way and the method of removal may be dependent upon thecomposition of the porogen layer. Exemplary methods of removing all or aportion of the porogen layer include (but are not limited to): leaching,washing, etching, vaporizing, volatilizing, etc. For example, inembodiments where the porogen layer includes sodium chloride grains,some or all of the sodium chloride grains may be removed by leaching(e.g., dissolving all or a portion of the porogen layer with aparticular solvent).

As will be understood by one of ordinary skill in the art, any portionof the porogen layer may be removed. In various embodiments, the desiredfinal product may include a solid polymer portion, a matrix layer, and aporous layer. In these embodiments, only a portion of the porous layermay be removed (e.g., to a certain depth), leaving a structure includinga solid polymer layer, a matrix layer (including the polymer andporogen) and a porous polymer layer. In some embodiments, the desiredstructure does not include any of the porogen layer and substantiallyall of the porogen layer is removed, resulting in a structure thatincludes a solid polymer and a porous polymer layer. In embodimentswhere the matrix layer is the desired outcome, this step 130 may beomitted.

FIG. 2 depicts an exemplary process for producing a porous polymer undercertain conditions. In particular, FIG. 2 shows a polymer sample placedin contact with a packed array of porogen (sodium chloride) grains atstep 1. In this particular example, the porogen grains are arranged at adepth of approximately 0.2 to 2 mm. In various embodiments, thearrangement of porogen grains affects the arrangement of pores in aresulting porous layer of the polymer sample and thus, the depth may beany suitable depth depending on the desired depth of pores or of aresulting matrix layer. For example, porogen grains may be arranged atdepths of approximately 0.05 mm to 5 mm or any suitable range inbetween.

Continuing with step 1, the surface of the polymer in contact with theporogen grains is heated to a particular processing temperature under aninitial pressure of about 2 PSI. In various embodiments, the particularprocessing temperature is below a melting point of the polymer. Forexample, as discussed below, PEEK exhibits melting temperatures atapproximately 240 and 343 degrees Celsius.

As will be understood by one of ordinary skill in the art, the initialpressure may be any suitable initial pressure. In various embodiments,the initial pressure is about 0.1 to 10 PSI. In some embodiments, theinitial pressure and the final pressure are the same (e.g., the samepressure is held constant throughout the entire process).

At step 2, once the polymer surface is heated to the processingtemperature, additional pressure is applied to the polymer. Inparticular embodiments, the processing temperature and the additionalpressure is held for a predetermined processing time and, as shown instep 3, the porogen is displaced within the surface of the polymer,creating a pore network (e.g., under particular conditions, the polymerflows between the porogen). According to various embodiments, theprocessing time is for about zero (0) to 45 minutes. In one embodiment,the processing time is for about 30 minutes.

The additional pressure may be any suitable pressure. In particularembodiments the additional pressure is up to 250 PSI. In one or moreembodiments, the additional pressure is between 50 and 250 PSI. In atleast one embodiment, the additional pressure is about 150 PSI.

At step 4, the additional pressure and heat are removed from the polymerand the polymer surface is cooled in a controlled fashion to managesolidification and crystallization. At step 5, the porogen grains areleached, leaving behind a thin porous surface layer that is integrallyconnected with the solid polymer body. Precise control of localtemperature, pressure, and time may achieve desired pore layercharacteristics. As will be understood by one of ordinary skill in theart, as shown in step 6, the introduction of surface porosity may resultin expansion of the total polymer structure, indicated by the change inheight, Δh.

Exemplary PEEK Data

As will be further discussed herein, PEEK exhibits melting properties attwo temperatures under particular conditions. As shown in FIG. 3, PEEKexhibits several thermal transitions in this differential scanningcalorimetry (DSC) scan. The first (lowest temperature) transition is theglass transition, which is characterized by a shift in the heat capacityof the polymer. As shown, this glass transition occurs at approximately145 degrees Celsius.

Continuing with FIG. 3, PEEK displays higher temperature transitions,characteristic of melting (e.g., endotherms). As will be understood byone of ordinary skill the art, the enthalpy of melting, the increasedheat energy required to overcome the crystalline order, is shown by thearea of the endotherm. Notably, in the embodiment shown in FIG. 3, PEEKshows a double melting behavior under these conditions with a small(lower temperature) endotherm and a large (higher temperature)endotherm. As shown, the first endotherm is measured at approximately240 degrees Celsius and the second endotherm is measured atapproximately 343 degrees Celsius. This “double peak” behavior has beenexplained as a two-stage melting process occurring due to varying sizecrystallites. However, it should be noted that melting occurs over arange of temperatures and the melting temperature (Tm) is generallydetermined from the temperature corresponding to the peak maximum of thesecond melting endotherm (e.g., 343 degrees Celsius, shown here). Itshould also be noted that endotherms for samples of a polymer may varybased on crystallinity of the polymer; thus, samples of the same polymermay have slightly varying endotherms based on slightly differentcrystalline structures (e.g., one PEEK sample may have a first endothermat 239.5 degrees Celsius and a second PEEK sample may have a firstendotherm at 241 degrees Celsius).

Exemplary Shear Strength Data

FIGS. 4A and 4B, show exemplary shear strength for PEEK measured overprocessing times of zero (0) to 30 minutes. As shown in FIGS. 4A and 4B,resulting interfacial shear strength between the porous layer and solidpolymer body increases with longer processing times above apredetermined processing temperature (Tp). In particular, FIGS. 4A and4B show that shear strength between the porous layer and solid polymerbody increases substantially linearly with increased processing timesbetween zero (0) and 30 minutes at temperatures of Tp. Tp in thisinstance is 330 degrees Celsius, which, as depicted in FIG. 3 anddiscussed above, is below the 343 degrees Celsius melting point of PEEK.

FIGS. 5A and 5B show exemplary shear strength for PEEK measured overprocessing times of about zero (0) to 40 minutes. As shown in FIGS. 5Aand 5B, the shear strength of PEEK potentially begins to plateau betweena processing time of around 30 to 40 minutes. Particularly, the shearstrength of PEEK is significantly correlated statistically (i.e. p-valueless than 0.05 as calculated by linear regression analysis) withprocessing time above a defined processing temperature of about 330degrees Celsius (which is thirteen degrees lower than the meltingtemperature for PEEK of 343 degrees Celsius) for up to about 30 to 45minutes.

Exemplary Pressure Data

FIGS. 4C and 4D show pressure data verses time above processingtemperature (Tp), while holding a constant polymer flow rate (asdiscussed herein, polymer flow may refer to polymer flow below a meltingtemperature of the polymer). The polymer flow rate may be any suitablerate, such as approximately two (2) mm/minute. As will be understood byone of ordinary skill in the art, FIGS. 4C and 4D (and 5C and 5D) depictpressures trending in a negative direction, which indicates an increasein pressure acting in compression. It should be understood that anincrease in pressure may be shown as positive or negative.

FIGS. 4C and 4D provide a potential explanation for the substantiallylinear increase in shear strength with increased processing time above aspecified processing temperature as shown in FIGS. 4A and 4B (about 330degrees Celsius in this instance, which is below the 343 degrees Celsiusmelting temperature of PEEK). In particular, the increased shearstrength may be due to an increase in polymer flow viscosity. As will beunderstood by one of ordinary skill in the art, polymer flow viscositytypically decreases or remains constant as it is heated for longerperiods of time. However, as shown in FIGS. 4C and 4D, pressure appliedto exert polymer flow at a constant rate is significantly correlatedstatistically (i.e. p-value less than 0.05 as calculated by linearregression analysis) with processing time above a defined processingtemperature of about 330 degrees Celsius for up to 30 to 45 minutes.This correlation is counter to expected results and indicates thatpolymer flow viscosity increases with processing time below 343 degreesCelsius. This phenomenon appears to plateau around 30 to 45 minutes asshown in FIGS. 5C and 5D.

As will be understood by one of ordinary skill in the art, FIGS. 4C, 4D,5C, and 5D show data based on holding a constant rate of polymer flow(e.g., polymer flow is held constant and pressure applied to hold thepolymer flow constant over time is measured), but this process mayoperate in the reverse. In various embodiments, pressure is known andapplied linearly to keep polymer flow constant.

Exemplary Wettability Data

As shown and described herein, in various embodiments, wettability viahydroxyl/carboxyl group % increases at the surface is shown to beindependently controllable independent of substrate or porogen type andpressure applied to the interface. This potentially contradicts earlierwork claiming dependence on surface energy of the substrate surface. Tothe contrary, shown herein are increases in hydroxyl % and wettabilitythereby that is independent of surface energetics of the substrate orpressures applied, and instead is heavily dependent on a controlledheating and cooling rate of the infiltrating and recrystallizing PEEK.

FIGS. 6A, 6B, and 6C show XPS O1s spectra of a polymer in an unprocessedstate and processed in various ways, including at least substantiallyprocessed in accordance with the processes described herein. In aparticular embodiment, as shown in FIG. 6A, unprocessed polymers (e.g.,PEEK) exhibit a peak at 535 to 530 eV. Generally, this peek may beexplained by the presence of the carbon to oxygen single and doublebonds as would be expected in PEEK (e.g., with ether and ketone groups,respectively), with more carbon to oxygen single bonds present thandouble bonds. In a particular embodiment, as shown in FIG. 6B, theporous surface of processed polymers (e.g., PEEK) exhibit a differentpeak at 535 to 530 eV, with a noticeable shift to lower binding energy.Generally, this peek may be explained by the presence of oxygen tohydrogen single bonds (e.g., hydroxyl groups) in addition to the carbonto oxygen single and double bonds as would be expected in PEEK, with theconcentration of oxygen to hydrogen single bonds between that of thecarbon to oxygen single and double bonds. In a particular embodiment, asshown in FIG. 6C, the porous surface of processed polymers after gammasterilization (e.g., PEEK) also exhibit a different peak at 535 to 530eV, with a noticeable shift to lower binding energy. Generally, thispeek may be explained by the presence of oxygen to hydrogen single bondsin addition to the carbon to oxygen single and double bonds as would beexpected in PEEK, with the concentration of hydroxyl groups exceedingthat of the carbon to oxygen single and double bonds.

FIGS. 6D and 6E show tables with atomic and molecular percentages fromthe XPS O1s spectra of a polymer in an unprocessed state and processedin various ways, including at least substantially processed inaccordance with the processes described herein. In various embodiments,the carbon to oxygen atomic ratio does not change in processed polymers,but there is an increased percentage of hydroxyl groups afterprocessing.

In various embodiments, as shown in FIG. 6D, the unprocessed polymers(e.g., injection molded and extruded PEEK) comprise approximately 0%hydroxyl groups, 70% ether groups, and 30% ketone groups. In aparticular embodiment, the injection molded PEEK comprises 65.65% ethergroups and 34.34% ketone groups but may comprise 60-70% ether groups and30-40% ketone groups. Similarly, in a particular embodiment, theextruded PEEK comprises 70.06% ether groups and 29.93% ketone groups butmay comprise 65-75% ether groups and 35-45% ketone groups.

In various embodiments, as shown in FIG. 6D, the processed polymers(e.g., porous PEEK and porous PEEK after gamma sterilization) compriseapproximately 50% hydroxyl groups, 30% ether groups, and 20% ketonegroups. In a particular embodiment, the porous PEEK comprises 48.42%hydroxyl groups, 31.48% ether groups, and 20.09% ketone groups but maycomprise 40-60% hydroxyl groups, 20-40% ether groups, and 10-30% ketonegroups. Similarly, in a particular embodiment, the porous PEEK aftergamma sterilization comprises 50.50% hydroxyl groups, 28.95% ethergroups, and 20.53% ketone groups but may comprise 45-55% hydroxylgroups, 25-35% ether groups, and 15-25% ketone groups.

In various embodiments, as shown in FIG. 6E, the unprocessed (e.g.,injection molded and extruded PEEK) and processed polymers (e.g., porousPEEK and porous PEEK after gamma sterilization) comprise similar carbonto oxygen atomic ratios (e.g., carbon to oxygen atomic ratio of 3.3 forthe processed polymers and 3.4 for the unprocessed polymers). In aparticular embodiment, the injection molded PEEK comprises 79.97% carbonatoms and 20.02% oxygen atoms but may comprise 75-85% carbon atoms and15-25% oxygen atoms. Similarly, in a particular embodiment, the extrudedPEEK comprises 84.39% carbon atoms and 15.6% oxygen atoms but maycomprise 80-90% carbon atoms and 10-20% oxygen atoms. In a particularembodiment, the porous PEEK comprises 79.82% carbon atoms and 20.18%oxygen atoms but may comprise 75-85% carbon atoms and 15-22% oxygenatoms. Similarly, in a particular embodiment, the porous PEEK aftergamma sterilization comprises 84.17% carbon atoms and 15.83% oxygenatoms but may comprise 80-90% carbon atoms and 10-20% oxygen atoms.

FIG. 7A shows exemplary wettability data of a polymer in an unprocessedstate and processed in various ways, including at least substantiallyprocessed in accordance with the processes described herein. As will beunderstood by one of ordinary skill in the art, a decrease in thecontact angle of a fluid (e.g., water) on the surface of a solid (e.g.,PEEK) indicates an increase in the wettability of the solid. As shown inFIG. 7A, the wettability of unprocessed PEEK is relatively low, with acontact angle of at least 70 degrees. Further, as also shown in FIG. 7,the wettability of PEEK that has only been thermally treated and did notcome into contact with a salt porogen is also relatively low, with acontact angle of at least 70 degrees. Continuing with FIG. 7, thewettability of PEEK that came into contact with a salt porogen (with orwithout pressure) is relatively high, with a contact angle below 52degrees. In a particular embodiment, the wettability of PEEK that cameinto contact with a packed salt porogen with pressure is also relativelyhigh, with a contact angle below 27 degrees. The wettability of a porouspolymer produced in accordance with the processes described herein(e.g., “Surface Porous PEEK Cage” in FIG. 7A) is very high, with acontact angle of about 0 degrees.

FIG. 7B shows exemplary roughness data of salt crystals and a polymerafter various processing. As will be understood by one of ordinary skillin the art, a fluid may wick into pores of a porous surface. Thus, theroughness of a surface may be thought to be the primary contributor towettability. As shown in FIG. 7B, the roughness for an extruded polymer(“EXTRUDED PEEK”), a polymer pressed against a single crystal salt(“PEEK THERMALLY TREATED 340 C AGAINST SINGLE CRYSTAL SALT”), and apolymer thermally treated without salt (“PEEK THERMALLY TREATED 340 CAIR”) are similar. Further, the roughness of salt crystals (“SALTCRYSTALS”) is similar to that of a polymer pressed against pack saltwith pressure (“PEEK AGAINST PACKED SALT WITH PRESSURE”). The roughnessfor a polymer substantially processed in ways described herein, as shownin FIG. 7B as “SURFACE POROUS PEEK CAGE”, has a higher roughness thanthe other samples shown.

After processing as described herein, surface porous polymers, invarious embodiments, have average roughness values greater than that ofthe porogen, salt crystals likely because the height/depth of the porewall may increase the roughness (e.g., the roughness of SURFACE POROUSPEEK CAGE is greater than the other samples). Further, according toparticular embodiments, macroscopically flat samples, either PEEK sheetpressed against packed flat salt or PEEK sheet pressed against singlecrystal salt, show roughness values similar to that of salt crystals andexhibit lower contact angles. As shown in FIG. 7B, extruded PEEK andPEEK thermally treated without salt have similar roughness values andexhibit similar contact angle values.

However, as shown in FIG. 7A, the contact angle for a polymersubstantially processed in ways described herein (“SURFACE POROUS PEEKCAGE”) has a much lower contact angle (e.g., about zero degrees). Thissuggests that the lower contact angle of the polymer substantiallyprocessed in ways described herein, and therefore with increasedwettability, may be due to changes in composition of the porous polymers(e.g., chemical changes of the surface of the polymer) and an increasedroughness of the surface (e.g., physical changes of the surface),opposed to an increase in roughness due only a physical change.

Exemplary Hydroxyl Group Data

FIGS. 8A, 8B, 8C, 8D, 8E show exemplary hydroxyl group data of anexemplary porous polymer (e.g., PEEK) produced in accordance with theprocesses described herein. As discussed herein, increasedhydroxyl/carboxyl % may indicate increased wettability. Further, asdiscussed herein, heat treatment appears to be the main factor in theincrease of hydroxyl %, and therefore, wettability. Specifically, in oneembodiment, the heating of the polymer to the processing temperaturesdiscussed herein results in an increased percentage of hydroxyl groupsin the porous surface of the polymer in comparison to the body of thepolymer or an unprocessed polymer.

FIG. 8A depicts a bar graph comparing hydroxyl group % of porous polymerheated in various ways. In the embodiment shown in FIG. 8A, surfacesthat were heated to a temperature just below (e.g., approximately 340degrees Celsius), at, or above about 343 Celsius (e.g., a meltingtemperature of PEEK), flowed onto a salt porogen, then cooled down hadan increase in hydroxyl % (carboxyl %). As shown in the embodiment inFIG. 8A, devices made from a polymer (e.g., PEEK) on a hot press (e.g.,a hot press with a heating rate of approximately 100 to 200 degreesCelsius per minute) for four (4) minutes above 343 Celsius, and at acooling rate of approximately 20 to 50 Celsius per minute with localizedheating, showed an increase in hydroxyl/carboxyl % (as shown at“CageTop” and “CageBottom”) over the body of the device or injectedmolded devices (e.g., “CageBulk” and “Injection Mold”). Further, devicesmade in an oven (e.g., an oven with a heating rate of about 10 to 20degrees Celsius per minute) for about 45 minutes above 343 Celsius andthen cooled at a rate of about 5 to 10 Celsius per minute.

FIG. 8B shows a bar graph representing hydroxyl group percentages forporous polymers cooled or recrystallized against different substrates,including salt (NaCl), CaCl₂, CaBr₂, Cal₂, Aluminum, and the hydroxylgroup % of the polymer when a device is created through injectionmolding (e.g., without the processes described herein). As shown in theembodiment in FIG. 8B, it appears that the hydroxyl group % isrelatively unchanged, regardless of the substrate used. This maycontradict previous findings suggesting that substrates affectwettability.

FIG. 8C shows a bar graph representing hydroxyl group percentages ofporous polymers recrystallized again various substrates with pressureapplied and without pressure applied. As shown in the embodiment in FIG.8C, the hydroxyl group percentage is increased with the use of salt inthe process (e.g., “Pressure FlatSalt” and “No Pressure FlatSalt”), butpotentially not as significantly as the heating and cooling process.

FIG. 8D shows a bar graph representing hydroxyl group percentages ofporous polymers cooled at different rates (e.g., after heating asdescribed herein). As shown in this embodiment, quenching, quenched thenannealed, and slow cooling does not affect the hydroxyl/carboxyl % ofthe porous polymer after heating and processing as described herein.

FIG. 8E shows a bar graph depicting hydroxyl group percentages of porouspolymers heated at two different temperatures (180 degrees Celsius and340 degrees Celsius) with and without single crystal salt contact. Inthe embodiment shown in FIG. 8E, a sample of a porous polymer that isnot in contact with salt (e.g., “Air”) heated to about 180 degreesCelsius (via a hot plate) shows hydroxyl group percentages of about 25to 40. In particular embodiments, the sample heated to 180 degreesCelsius, without salt contact, may have a hydroxyl group percentage ofabout 32.1 or about 27.5 to 36.7.

Continuing with the embodiment shown in FIG. 8E, a sample of porouspolymer that is not in contact with salt (e.g., “Air”) heated to about340 degrees Celsius (via a hot plate) shows hydroxyl group percentagesof about 45 to 65. In particular embodiments, the sample heated to 340degrees Celsius, without salt contact, may have a hydroxyl grouppercentage of about 54.9 or about 48.1 to 61.7.

FIG. 8E further depicts a sample porous polymer that is contact withsalt (e.g., “Salt”) heated to about 180 degrees Celsius having hydroxylgroup percentages of about 20 to 35. In one or more embodiments, thesample heated to about 180 degrees in contact with salt may have ahydroxyl group percentage of about 27.6 to about 22.4 to 32.8.

FIG. 8E also depicts a sample porous polymer that is contact with salt(e.g., “Salt”) heated to about 340 degrees Celsius having hydroxyl grouppercentages of about 40 to 60. In one or more embodiments, the sampleheated to about 340 degrees in contact with salt may have a hydroxylgroup percentage of about 50.8 to about 42.9 to 58.7.

Exemplary Porous Layer Data

FIGS. 9A and 9B show porous layer data of an exemplary porous polymer(e.g., PEEK) produced in accordance with the processes described hereinas measured with a direct distance transformation method frommicrocomputed tomography scans at a consistent threshold. As shown inthe embodiment depicted in FIG. 9A, the porous layer includes aplurality of substantially spherical pores extending through the solidbody for a defined distance (e.g., from 0.5899 mm to 0.8478 mm). In aparticular embodiment, the pore layer thickness (e.g., the defineddistance) is approximately 0.6911 mm. In particular embodiments, theporogen structure depends upon the shape of the porogen material and thearrangement of the porogen. Thus, the pores may be irregular (e.g., notin a defined pattern) or regular (in a defined pattern).

Continuing with the embodiment shown in FIG. 9A, the pores are separatedby struts that define the shape of the pores. According to oneembodiment, the strut spacing (e.g., pore size) is between about 0.2158mm and 0.2355 mm. In a particular embodiment, the strut spacing is about0.1 to 0.5 mm. In some embodiments, the strut thickness is between about0.0945 mm and 0.1132 mm. In further embodiments, the strut thickness isbetween about 0.05 mm and 0.20 mm. In a particular embodiment, the strutspacing is approximately 0.2266 mm, and the strut thickness isapproximately 0.1019 mm.

In the embodiment shown in FIG. 9B, the porosity of the porous layer isbetween 62.57% and 64.97%. In a particular embodiment, the porosity isapproximately 63.59%. In a further embodiment, the porosity isapproximately 0.1 to 65%. In one embodiment, interconnectivity betweenthe pores is between 99.0754% and 99.981%, and in a particularembodiment, the interconnectivity is approximately 99.87%. In stillfurther embodiments, the interconnectivity is about 40.0 to 99.9%. Aswill be understood by one of ordinary skill in the art, poreinterconnectivity of approximately 99% indicates that substantially allpores are connected and all porogen has been leached/removed from thepolymer (e.g., as described herein).

Exemplary Expulsion Force Data

FIG. 10 shows expulsion force data of an exemplary device including aporous polymer (e.g., PEEK) produced in accordance with the processesdescribed herein. In various embodiments, as shown in FIG. 10, theexpulsion force that may displace a device comprising a porous polymeras produced by processes discussed herein exceeds 150 N. In a particularembodiment, the expulsion force is at least 178 N and may be as high as200 N, if the device also includes ridges in its porous surfacestructure. In contrast, in a particular embodiment, the expulsion forcethat may displace a device comprising an unprocessed polymer does notexceed 140 N and may be as low as 60 N. As will be understood by one ofordinary skill in the art, expulsion resistance (force, as measured inNewtons) is a function of a coefficient of friction and the normal forceapplied. Thus, devices with porous surfaces created by processesdescribed herein should have similar expulsion resistance, regardless ofthe size or shape of the device.

Exemplary Use Cases

Materials created from the processes described herein may have a widevariety of uses. In particular embodiments, the processes describedherein may be beneficial in any application where it is desired toadhere a material to the second material with different properties(e.g., adhere a first polymer with a first stiffness to a second polymerwith a second stiffness). Such as, for example, adhering a soft polymer(e.g., polyethylene, polyvinyl-alcohol, or polycarbonate-urethane) to aharder polymer such as PEEK. This example may be applicable for knee orhip replacements. As a second example, porous polymers may be used inmedical devices and more particularly for orthopedic applications topromote tissue ingrowth. Other exemplary uses may be aerospace,automotive, and other fields.

FIGS. 11A, 11B, and 11C show one non-limiting, exemplary embodiment of amedical device comprising the materials created from the processesdescribed herein. As will be understood, the example is for discussionpurposes only and should not be considered to be limiting of the types,shapes, sizes, etc. of devices that may be manufactured by the processesor have the features or properties described herein.

As shown in FIG. 11A, in a particular embodiment, the processesdescribed herein are used to create a spinal implant 1101 that ishexahedral in shape with at least one porous layer. In one embodiment,the spinal implant 1101 comprises two substantially square-shaped porousfaces that are substantially parallel to one another with oneconvexly-curved side 1103, as shown in FIG. 11A. In a particularembodiment, as shown in FIGS. 11B and 11C, the two porous faces, 1109and 1113, are angled slightly inwards towards each other. Between thetwo porous faces is a body layer 1111 of varying thicknesses. Returningto FIG. 11A, the spinal implant 1101 may include an inner void 1105 thatis in substantially the same shape as the two porous faces and extendsfrom the surface (e.g., 1115) of one of the porous faces (e.g., 1109)through the surface (e.g., 1119) of the other porous face (e.g., 1113).

As will be appreciated by one having ordinary skill in the art, thespinal implant may be produced in different sizes and shapes toaccommodate different patients, implant locations, etc. (e.g., largerimplants for patients with larger anatomies, smaller implants forpatients with smaller anatomies, larger implants for use in the lumbarvertebrae, smaller implants for use in the thoracic vertebrae, etc.).Similarly, although not shown in the figures, the spinal implant may besubstantially cylindrical in shape, substantially cubic in shape,substantially rectangular in shape with a pyramidal nose, substantiallyhalf-moon in shape, substantially solid with no voids, substantiallyhollow with multiple voids of varying shapes and sizes, include ridgeson the porous surfaces of varying widths and heights, etc.

As will be understood by one of ordinary skill in the art, the spinalimplant (or other device) may be made from a radiolucent material, suchas PEEK. Thus, according to one embodiment, as shown in FIGS. 11A, 11B,and 11C, the spinal implant further includes one or more markers 1107for detection of tissue ingrowth (e.g., bone) into the implant. Forexample, in one embodiment, the implant may include two tantalum markers1107 that are substantially-cylindrical in shape (these markers,however, may be any suitable shape, such as rectangular, triangular,conical, etc.). Generally, the markers are positioned so that theyextend vertically through the implant with the circular end-surfaces ofthe marker, 1117 and 1121, substantially flush with the top of porousfaces, 1115 and 1119, as shown in FIGS. 11B and 11C. In anotherembodiment, although not shown, the end-surfaces of the marker, 1117 and1121, are angled so that they are even with the top of porous faces,1115 and 1119. Thus, to determine tissue ingrowth, radiography oranother electromagnetic-imaging technique is used to take a lateral viewof the implanted spinal implant. By determining the position of the endsof the markers, 1117 and 1121, in the image and comparing them to thelocation of the edges of the tissue in the image, the amount of tissueingrowth may be determined. Specifically, because the ends of themarkers, 1117 and 1121, are at the edges of the porous surface of thespinal implant, 1115 and 1119, any tissue that extends past the ends ofthe markers should represent tissue ingrowth into the spinal implant. Aswill be appreciated by one having ordinary skill in the art, multipleimages of the same spinal implant taken at different times may becompared to determine the change in tissue ingrowth, rate of tissueingrowth, etc.

Further, as will be understood by one having ordinary skill in the art,a marker (e.g., marker 1107) may be of any suitable material orconstruction. In various embodiments, the marker may be made of aradiolucent material, but include a radiopaque additive (e.g., bariumsulfate or bismuth compounds). In one or more embodiments, the markermay be made form a suitable radiopaque metal.

Because the amount of tissue ingrowth may be determined, a strength ofthe bond between the tissue and an implant may be calculated/inferred(e.g., any orthopedic implant, including, for example, the implantdescribed above). In various embodiments, this could be used todetermine, based on amount of measurable tissue ingrowth, when a personwith a spinal implant may be able to safely resume load-bearingactivities.

In various embodiments, as described above, a clinician may beinstructed to take a radiograph of a spinal implant that includes theabove described markers and porous layer. The clinician may be furtherinstructed to measure the distance the tissue has grown into theimplant, based on the distance the tissue has grown past the top (orbottom) of the markers. In this way, the distance the tissue has grownpast the markers may be correlated to a strength of adhesion of theimplant to the surrounding tissue (e.g., bone), which may give anindication of when the person with the implant may be able to performcertain activities, with a lower risk of further injury.

CONCLUSION

The foregoing description of the exemplary embodiments has beenpresented only for the purposes of illustration and description and isnot intended to be exhaustive or to limit the inventions to the preciseforms disclosed. Many modifications and variations are possible in lightof the above teaching.

The embodiments were chosen and described in order to explain theprinciples of the inventions and their practical application so as toenable others skilled in the art to utilize the inventions and variousembodiments and with various modifications as are suited to theparticular use contemplated. Alternative embodiments will becomeapparent to those skilled in the art to which the present inventionspertain without departing from their spirit and scope.

What is claimed is:
 1. A method comprising: obtaining or causing toobtain an image of an implanted spinal implant in a patient, usingradiography or another electromagnetic imaging technique, wherein thespinal implant comprises: a body having a first porous surface layer; aninner void extending through a thickness of the body and the firstporous surface layer at a center of the spinal implant; and and a firstmarker positioned to extend vertically through a thickness of the bodyand the first porous surface layer, the first marker being configured tobe detected using radiography or another electromagnetic imagingtechnique; determining a position of an end of the first marker in theimage; determining a location of an edge of a tissue in the image;comparing the position of the end of the first marker with the locationof the edge of the tissue in the image; and determining an amount ofingrowth of the tissue into the spinal implant, wherein the end of thefirst marker is disposed approximately at an edge of the porous surfaceof the spinal implant, and any tissue that extends past the end of thefirst marker into the spinal implant represents tissue ingrowth.
 2. Themethod of claim 1, further comprising, prior to obtain or causing toobtain the image, implanting the spinal implant into an intervertebralspace in a spine of the patient.
 3. The method of claim 1, wherein theimage is a lateral view image.
 4. The method of claim 1, wherein theimage is obtained using radiography.
 5. The method of claim 1, whereinthe first porous surface layer comprises a plurality of pores, each porein the plurality of pores extending a defined distance from a first faceinto the body.
 6. The method of claim 1, wherein the body comprises amaterial having a first particular percentage of hydroxyl groups, andwherein the first porous surface layer comprises a material having asecond particular percentage of hydroxyl groups, the second particularpercentage of hydroxyl groups being greater than the first particularpercentage of hydroxyl groups.
 7. The method of claim 1, wherein thespinal implant further comprises a second porous surface layer disposedon an opposite side of the body from the first porous surface layer, andwherein the first marker is positioned to extend vertically through athickness of the first porous surface layer, the body, and the secondporous surface layer.
 8. The method of claim 7, wherein the first markerextends from an upper face of the first porous surface through the bodyto a bottom face of the second porous surface.
 9. The method of claim 8,wherein the first marker is positioned such that it extends verticallythrough the body and the first and second porous surfaces, and each endthe first marker is substantially flush with the upper face of the firstporous surface and the bottom face of the second porous surface,respectively.
 10. The method of claim 1, wherein the first markercomprises a radiopaque metal.
 11. The method of claim 10, wherein theradiopaque metal is tantalum.
 12. The method of claim 1, wherein thefirst marker comprises a radiolucent material and a radiopaque additive.13. The method of claim 12, wherein the radiopaque additive comprisesbarium sulfate or a bismuth compound.
 14. The method of claim 1, whereinthe tissue is a bone.
 15. The method of claim 1, wherein the firstmarker is substantially cylindrical, rectangular, triangular, or conicalin shape.
 16. The method of claim 1, wherein the implant furthercomprises a second marker positioned to extend vertically through athickness of the body and the first porous surface layer, the secondmarker being configured to be detected using radiography or anotherelectromagnetic imaging technique.
 17. The method of claim 1, whereinthe body comprises polyetheretherketone (PEEK).
 18. The method of claim1, further comprising: correlating the amount of tissue ingrowth with astrength of adhesion of the spinal implant to the tissue.
 19. The methodof claim 18, further comprising: determining, based one or more of thestrength of adhesion of the spinal implant to the tissue, or the amountof tissue ingrowth into the spinal implant, when or whether the patientmay be able to safely perform or resume an activity.
 20. The method ofclaim 19, further comprising: upon determining that the patient maysafely perform or resume load—the activity, providing the patient with arecommendation or a clearance to resume or perform the activity.